While there has been some variation of spark plug design over time, the conventional spark plug basically remains the same, being comprised of a cylindrical metal shell whose terminal end is threaded to permit installation and removal at the engine's cylinder head, said shell containing a core insulator that surrounds a center electrode, said core insulator and center electrode extending from the threaded end of shell to the distal end of spark plug, said center electrode projecting through the end of core insulator forming an electrical terminal that is designed to connect with a high tension lead wire. At the proximal end of the spark plug as defined by the threaded end portion of shell, said center electrode projects through the end of core insulator a distance necessary for interaction with the ground electrode, said ground electrode extending from the rim of the shell's end portion parallel to the longitudinal axis of the center electrode, making a 90.degree. bend at a distance that allows the end portion of ground electrode to terminate at right angle beyond and in line with the flat end portion of center electrode defining a suitable spark gap.
By definition a spark plug can be said to be an engine component that provides, within the combustion chamber, a spark gap that conducts high tension electrical energy for the purpose of igniting a fuel and air mixture.
In research it has been noted that electrode design of a spark plug will affect its performance.
With regard to experiments in this area, it is my conclusion that the spark plug itself is a hindrance to the purpose for which it is designed and that the ideal condition for best results would be for a spark to occur centrally within the combustion chamber with no barriers or protrusions of any kind, allowing the flame kernel to propagate equally and undisturbed in all directions throughout the combustion chamber. If this were possible, it would greatly improve engine performance and reduce hydrocarbon emissions. As this will probably never be achieved, it follows that a spark plug design that could at least approximate such a condition should be desired.
In conventional spark plug when viewed from the terminal or sparking end, two blind spots can be observed, that is two areas that are blocked by the ground electrode preventing and deflecting flame travel. One longitudinally outward from the center electrode where the ground electrode is necessarily defining a spark gap but at the same time shadowing the flat end portion of the center electrode blocking and deflecting flame travel. The other is radially where the vertical portion of the ground electrode shadows the vertical end portion of the center electrode blocking and deflecting lateral flame travel. The more bulky and wider the ground electrode, the more pronounced is this effect. It follows that any design that reduces the shadow effect of the ground electrode would be an improvement over prior art.
With regard to prior art, U.S. Pat. No. 4,268,774 in FIG. 6 of drawing sheet shows an improved design of a ground electrode for an otherwise conventional spark plug, the electrode having diverging prongs, that according to the inventor, causes a unique arcing action in the spark gap, resulting in lower carbon monoxide emissions. Tests of this spark plug in an '84 Mazda (4 cyl. Engine) at a certified emission test station with computer print out bears out the inventor's claim as being valid. The same test made using a conventional spark plug with my replaceable double ended ground electrode also registered a reduction of emissions in the computer print out.